The present invention relates to routing area updates (RAUs) that take place as a mobile terminal moves from one radio access coverage area to another, and particularly to such movement when the mobile terminal is in a so-called standby mode in which no data is being transmitted or received.
GSM (Global System for Mobile Communications) radio coverage, which may also be referred to as second generation (2G) radio coverage, is quite extensive today. During the introduction of UMTS (Universal System for Mobile Telecommunications), which may also be referred to as third generation (3G) radio coverage, UMTS radio coverage is expected to be limited to urban areas. Thus UMTS radio coverage will cover only parts of the more extensive GSM radio coverage areas. Even within UMTS coverage areas, the UMTS radio coverage cannot be expected to be contiguous. For example, given that the frequency used for UMTS is higher than that for GSM, the in-building penetration will not be as good as GSM. This will result in small pockets (such as inside buildings) without UMTS coverage within the overall UMTS coverage area. Thus, only GSM radio coverage will be available in these pockets.
A dual mode GSM and UMTS mobile terminal (a mobile terminal is referred to as user equipment (UE) in UMTS) can communicate using either one of the two radio access systems. If a dual mode mobile terminal communicating via the UMTS radio link goes out of UMTS coverage, to an area with only GSM coverage, it can expect to continue the communication via the GSM radio link, but with a consequential degradation of service. Similarly a dual mode mobile terminal in an area with only GSM radio coverage which moves into an area with UMTS coverage can expect to switch to the UMTS radio link to improve service.
Thus as a dual mode mobile terminal moves around within radio access areas, changes in the type of radio access can be expected as the available radio access systems change. As the mobile terminal moves between radio access areas, routing area updates occur to notify the necessary support network of the new position of the mobile in the routing area associated with the particular radio access type. Changing between two radio access systems involves additional signalling and can also lead to outages during the transition between the two systems. The impact of the additional signalling and outages depends on the network architecture and the protocols chosen.
Packet data communication can be bursty, and there can consequentially be long periods when a mobile terminal is not sending or receiving data. When a mobile terminal is in packet communication mode in the GSM network, it is communicating via the GPRS interface. A certain time-out period after sending the last packet, the mobile terminal will transfer to a standby state. In the UMTS network, after a certain time out period of no activity, the terminal will first transfer to a so-called xe2x80x98UTRAN Registration Area (URA) connectedxe2x80x99 state. In the URA connected state, the connection between the mobile terminal and the UTRAN is maintained on the Iu link. After a longer period of time, the context in the UTRAN which identified the link to the mobile can be removed and the Iu connection torn down. While the state of the mobile terminal after the Iu connection has been torn down has not been given any specific name in the UMTS standards, it shall be referred to herein as a UMTS standby state.
In the proposed implementations of both the GSM and UMTS standby states, a mobile terminal always performs a routing area update as it moves between radio access system coverage areas at all times, even when it is in the standby state.
The present invention provides an improved technique for reducing unnecessary routing area updates, which still ensures the location of a mobile terminal is known when the mobile terminal starts data communication after being in a standby state.
According to the present invention there is provided a packet radio access network architecture having a common routing area supported by first and second wireless access systems, wherein a mobile terminal moves between the first and second wireless access systems in the common routing area whilst no packet transmission is taking place, then no routing area update takes place.
If packet transmission is initiated, no routing area update may be required if the mobile is connected to the same wireless access system as in its previous packet transmission.
If packet transmission is initiated, a routing area update may take place if the mobile is connected to a different wireless access system than in the previous packet transmission. If packet transmission is initiated by the mobile, the packet transmission initiation may include the routing area update.
If the packet transmission is initiated by one of the wireless access systems, the mobile may receive a paging request. Responsive to the paging request the mobile may initiate a routing area update. The first and second wireless access systems may be GSM and UMTS access systems.
According to the present invention there is provided a method of controlling routing area updates within a common routing area supported by first and second wireless access systems, wherein if a mobile terminal moves between first and second wireless systems in the common routing area whilst no packet transmission is taking place, then no routing area update takes place.
If packet transmission is initiated, no routing area update may take place if the mobile is connected to the same wireless access system as in its previous packet transmission.
If packet transmission is initiated, a routing area update may take place if the mobile is connected to a different wireless access system than in the previous packet transmission.
If packet transmission is initiated by the mobile, the packet transmission initiation may include the routing area update.
If the packet transmission is initiated by one of the wireless access systems, the mobile may receive a paging request. Responsive to the paging request the mobile may initiate a routing area update.
The first and second wireless access systems may be GSM and UMTS access systems.
Thus a mobile terminal (or user equipment) moving back and forth between a 2G environment and a 3G environment without sending any data will not generate any signalling. This frequent switching between 2G and 3G environments is likely to happen at the edges of the patchy 3G coverage areas.
This allows almost all of the 2G and 3G implementation of the serving GPRS support nodes (SGSNs) to be kept separate. The routing area update (RAU) performed before sending any data from the new access network will result in the context transfer from the 2G to the 3G and also the set up of the proper state machines and protocol stack.